Apparatus for testing electrical devices



Dec. 6, 1949 s. BOCK APPARATUS FOR TESTING ELECTRICAL DEVICES Filed March 5, 1948 INVEN TOR 5. 806% A T TOR/V5 V Patented Dec. 6, 1949 APPARATUS FOR TESTING ELECTRICAL DEVICES Sam Bock, Baltimore, Md., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 3, 1948, Serial No. 12,716

This invention relates to apparatus for testing electrical devices, and more particularly to apparatus for testing coaxial units used in the manufacture of coaxial cables.

One type of coaxial unit comprises a center conductor positioned coaxially within an outer tubular conductor by means of non-conductive discs spaced uniformly along the central conductor so as to leave an air dielectric therebetween, and flexible steel tape wound spirally around the tubular conductor.

In the manufacture of such coaxial units, various types of conductive faults which produce a path of reduced dielectric strength across the air dielectric between the central and tubular conductors have been frequently encountered. Generally, various electrical tests are applied to each coaxial unit to ascertain the presence of such faults in order that they may be removed from the unit. It was found, however, that the physical position of the coaxial unit affected the ability of the electrical tests to locate any conductive faults present in the conductor. For instance, it was found that agiven length of coaxial unit wound on a reel would appear to be free of any faults for a given position of the reel, but would prove defective .when the position of the. reel was changed. It was further found that a coaxial unit, which had been: tested and found satisfactory, would, upon subsequent handling of the reel, prove to have conductive faults therein when subjected to final electrical inspection.

An object of the invention is to provide new and improved apparatus for testing electrical devices.

Another object of the invention is to providenew and improved apparatus for rotating and jarring a given length of coaxial unit while the conductors of the unit are subjected to a high potential difference.

The invention contemplates the provision of an apparatus for testing a given length of coaxial unit, wherein the central and outer conductors. of the coaxial unit are subjected to a high potential difference while the coaxial unit is simultaneously rotated and jarred to cause any conductive faults present in the unit to be positioned so as to produce a path of reduced dielectric strength between the central and outer conductors, whereby they may be detected.

A more complete understanding of the invention may be had from the following detailed description, when read in conjunction with the ap- I pended drawing, in which:

Fig. 1 is a side elevational view, partially in section, of a testing apparatus embodying fea- 2 Claims. (Cl. 219-11) tures of the invention and by means of which gethods embodying the invention may be pracced; 1

Fig. 2 is a front view of the apparatus shown in Fig. 1 having a portion thereof broken away for clarity;

Fig. 3 is an enlarged, fragmentary, sectional view taken along line 3-3 of Fig. 2;

Fig. 4 is an enlarged, fragmentary view of a coaxial unit to be tested by the methods and apparatus embodying the invention, and

Fig. 5 illustrates diagrammatically an electrical control circuit for apparatus comprising the invention.

Referring now to the drawing, and more particularly to Fig. 1, a testing apparatus indicated generally by the numeral 10, comprises an upper compartment H and a reel compartment i2. The compartment ll encloses various electrical. instruments and apparatus for detecting and locating conductive faultsthat may be present in coaxial cable units. The electrical apparatus mounted in the compartment. II and its associated circuits are fully disclosed and described in a copending application Serial No. 680,497, filed June 29, 1946, by R. D. Gambrill, now Patent No. 2,481,655, dated September 13, 1949. Since this testing apparatus forms no part of the present invention, it will be described only as fully as is necessary for a clear understanding of the invention.

The reel compartment .12 (Fig. 1) is provided with a ramp l3 atthe base thereof, which enables a reel "containing a predetermined length of coaxial unit l5 to be rolled into the compartment l2 so that it rests on an idler roller l6 suite ably journalled in bearings ll-i1 (Fig. 2) secured to the opposite sides of the compartment l2 and on a roller l 8 journalled in bearings i 9l3 secured to the sides of the compartment. A door 20 which is slidably mounted in the test set It], is shown in its uppermost position in Figs. 1 and, 2, and may be lowered so as to close the reel compartment 12 while various testing operations are performed'on the coaxial unit i5. The right hand end of the roller l8 (Fig. 2) extends beyond its associated bearing I9, and. is coupled to a gear reducer 22, which in turn is connected to and driven by an electric motor 23. The roller is is provided with an eccentric periphery (Fig. 3) formed by a minor diameter periphery 24 and a major diameter periphery 25, arranged to form a continuous surface except for a radial shoulder 26, which joins the periphery 2i and the periphery 25.

When the reel i4 is positioned on rollers i6 and ing purposes.

V is jarred sufficiently to cause any conductive particles within the coaxial unit to be jarred loose or be reoriented, so as to assume different positions in the air dielectric between the conductors (of the coaxial unit.

A flexible test lead 21 (Figs. 1 and 2) has one end thereof connected to theelectri'cal apparatus (not shown) positioned in the compartment H.

The other end of the lead 21 extends into the reel compartment I2 and is provided with .a spring clip 28 by means of which it is connected to a center conductor 29 (Fig. 3) prepared to extend beyond the inner end of the coaxial unit 15. The

inner end 30 of the coaxial unitis extended through an opening 3! (Fig. 2,) prouidedinithe" head of the reel l4 when the coaxial unit I5 liS wound on the reel l4 in order that the inner endof thezcoaxial-unit will be available for test- The center conductor 2.9 :positioned coaxially within anouter rtubnlar conductor 32 by means'of insulatingdiscs33-33 :s-paced uniformly along .the conductor 29.. The tubular conductor-32 hasrseveral flexible:steel tapes3'4-t3 i wound spirally therearound.

Inthe manufacture of coaxial units, such;as 'the coaxial uni-t I15, various types of conductive Efaults may be present in the coaxial unit, which provide paths -of reduced dielectric strength bethe coaxial-unit. The:conductivefaultmayresmt from loose metallic particles :3535 within the spaces between the discs?33-33 pr hair-like slivers 36-36 attached to the central conductor '29 or the tubular conductor 32.

Referring now to Fig. 55, the motor 23 is connected by means of atwo-wire circuit indicated generallygat 31 across terminals Eli-38 which may positioned across the opening of the-reel compartment. A two pole, single throwswitch 4'! is provided for controlling the continuity of the circuit 31 between the lampcfifl and the motor 23.

A time delay relay 42 has its operating-coil 43 connected across the circuit "34 --so as to be 'energized when the switch 4| is-closed. Theoperating coil .43 is arranged to :actuate' a-cam 44, which is provided with a recess '45 for receiving the end of a resilient arm 46. The cam 44 normally maintains the resilient arm 46 in engagement with 'a stationary contact 59 connected directly to one terminal-of the motor 23. A lam p'fil ,is connected across the portion of the circuit 3? controlled by the time delay relay 42, and serves to indicate when the arm 46 is in engagement with the contact 5 and likewise when 'the'motor. 23ris energized. When the switch 4| is closed, the operating coil 43, the lamp 5! and the motor v23 are simultaneously energized, whereupon the roller i8 is rotated to rotate the reel I4. 'The operating coil c3 of the relay 42' actuates the cam44 so as to cause the arm 46 to be disengaged from the contact after a predetermined period of time has elapsed, thereby terminating the operation of the motor 23.

Operation The purpose of the electrical apparatus (not shown) anountedfin the chmpar'tment 1;! I, which is fully described in the aforementioned co-pending application, is to determine whether any of the above-described faults are present in the coaxial unit l5.. The connection of the lead 21 .to the center conductor 29 serves to connect the center conductor to one side of a high potential IDaC. circuit embodied-in the electrical apparatus.

The opposite side -of the high potential circuit is grounded, and since the tubular conductor 32 is grounded through its contact with the steel tapes 3434 wound therearound and the reel H, the high potential is applied across the conductors 29 and 32 and any fault positioned in the air dielectric therebetween.

'lf thereare loose metallic p rticles, such as' the particles 35.35.,. resting on the inside surface of the tubular conductor .32, their position ma-yvbe such thatthey do not'reduce the-airrgap between the conductors :sufliciently %to permit ithe high potential to breakdown the air dielectric between the particle and the center conductor and the presence of :such particles would :not be detected. Likewise, if the. rhair-lilre metallic slivers 3636 were positioned substantially parallelto and close to the conductors 2.3 and 32 ne spectivel-y, that is, their full line positions as shown in Fig. 4, they would be detected by the high potential test. It is'therefore'necessary to change the position :of the coaxial unit 15 :to cause loose metallic particles, such .as particles 353:5, to assume a position on the insulating discs 33-33, and to jar-the coaxial unit .15 so :as to cause the hair-like slivers '36-'36 to assume their dotted line positions in the air dielectric, asshown-in Fig. 4, while the high potential test is being appliedacrossthe conductors 2'9'andi32. By placing the loose particles 35-3:5 :or the hair-like slivers 36-36 in their positions they will :pro-

vide a path of "substantially reduced dielectric strength betweenthe conductors 2 9 1 and .32, which will break "down 'under the stress of the high potential, and the presence of such faults willbe indicated by the -testing apparatus.

Assuming that the electrical testing apparatus (not shown) positioned in the compartment 11 of the testing apparatus i1) is properly energized and adjusted for testing coaxial units, such as the coaxial unit 15, the door 20 is raised to its upperinost position as'showmin Figs. "1 and 2, which actuates the-switches 39--39*to their open-posi tions. A reel 14, which holds 'aprede'termined length :of coaxial unit [5 having its inner end 30 projecting through the opening 3| provided in the adjacent head of the reel [4, is rolled up the ramp [3 and positioned on the rollers 1'16 and I8 (Fig. '2). The spring clip 28 attached to the end of the lead 21 is clipped to the centralconductor 29 extending beyond the inner end 30 of the coaxial unit l5, whereby the conductor 23 is connected to one side of the high D. C. potential testing circuit embodied in the electrical ,appa-- nection between the spring clip 28 and the central conductor 29.

The door then is lowered so as to close the reel compartment l2, whereby the switches 39-39 are actuated to their closed positions. Closure of the switches 39-39 energizes the lamp 4!! to indicate that the door is lowered and that the apparatus is in condition to permit further testing of the coaxial unit [5. Suitable switching means embodied in the electrical apparatus (not shown) positioned in the compartment I l is actuated to impress a high potential across the conductors 29 and 32 and any faults, such as the particles 35-35 or slivers 36-36, which may be.

present in the coaxial unit 15. The two pole switch ll then is actuated to its closed position, whereby the operating coil 48 of the time relay 42 is energized and starts its timing cycle on the cam 44. Since the cam id is in its starting position it maintains the resilient arm 48 in engagement with the contact 5% thereof and closure of the switch 4| places the motor 23 directly across the terminals 38-38 connected to a suitable potential source. The lamp 4!] is also energized by the switch 4| to indicate that the motor 23 is operating.

The motor 23 drives the roller l8 through the gear reducer 22 in a clockwise direction (Fig. 1) at a predetermined rate of speed. This rotation of the roller l8 serves to rotate the reel hi and the coaxial unit l5 wound thereon in a counterclockwise direction (Fig. 2) while the high potential is applied to the conductors 29 and 32. Upon each complete revolution of the roller l8 the coaxial unit I5 is jarred as the reel drops from the periphery to the periphery 24 of the roller IS. The perimeter of the roller [8 is of such length that the roller must be rotated a plurality of revolutions in order to effect one complete revolution of the reel l4, whereby the coaxial unit is jarred a plurality of times during one complete revolution of the reel.

This rotating and jarring of the coaxial unit l5 serves to position the loose metallic particles -45 or any hair-like slivers, such as slivers 36-45 that may be present in the coaxial unit so that they will provide a path of substantially reduced dielectric strength between the center conductor 29 and the tubular conductor 32 of the coaxial unit. When such faults are so positioned within the coaxial unit a breakdown of the air dielectric of the unit will occur at the faults which indicates the presence of such faults in the coaxial unit as it is being rotated by the motor 23.

The motor 23 remains energized and continues to rotate and jar the coaxial unit l5 until the cam Mi of the time delay relay has been rotated to such a position that the end of the resilient arm drops into the recess 45 of the cam. In so doing, the resilient arm 45 is disengaged from the stationary contact and thereby opens the cirsuit 3'! to the motor 23. This deenergizes the motor to terminate the rotation of the reel, and deenergizes the lamp 5|, which indicates that the timing period has elapsed. The time delay relay 42 may be adjusted to provide an operating period for the motor which will effect the desired rota tion and jarring of the reel I4 and the coaxial unit l5 carried thereby.

Let it be assumed that one complete revolution of the reel l4 and coaxial unit It is desired to be completed in one-half minute and that the reel is to be jarred fifty times during this period. The time delay relay 42 is then adiusted to delay open ng the circuit 3'! to the motor 23 for onehalf minute, and the motor speed is adjusted to rotate the roller I8 fifty revolutions per one-half minute. In this case, the roller I8 is designed to have a periphery of such length that fifty revolutions of the roller will rotate the reel i4 one completerevolution. Under these conditions, while the reel 14 is being rotated through one revolution, it likewise is being jarred fifty times as it drops from the periphery 25 to the periphery 24 of the roller 18. One complete revolution of the coaxial unit will serve to position any loose metallic particles, such as the particles 35-35, therein so that a breakdown will occur in the coaxial unit at the point where the particles are positioned. Jarring the coaxial unit fifty times in one revolution thereof also will cause the hair-like slivers 36-36 to assume their dotted line positions, as shown in Fig. 4, and thereby cause a breakdown to occur thereat, which serves to indicate their presence in the coaxial unit.

If the coaxial unit I 5 proves to be satisfactory while being rotated and vibrated the number of times permitted by a given setting of the time delay relay 42, the door 20 is lifted to its uppermost position, the lead 21 is disconnected from the central conductor 29 and the reel I4 is rolled out of the reel compartment I2 so that another reel containing a length of coaxial unit may be positioned therein. If the coaxial conductor l5 proves to be defective during the rotating and vibrating operation, other high potential testing operations are performed on the coaxial unit be-- fore the reel is removed from the reel compartment to burn out the faults and to locate the positions of faults which are not removed by the burn-out testing operation.

What is claimed is:

1. In a testing apparatus arranged to impress across the filamentary central conductor and the outer tubular conductor of a coaxial unit a D. C. potential having an intensity sufficient to break down any faults in the coaxial unit which provide paths of reduced dielectric strength between the conductors, the improvement which comprises a reel compartment in which a reel containing a coaxial unit which may be positioned, a cable suspended in the reel compartment for connecting the center conductor of the coaxial unit to the D. C. potential testing apparatus, an idler roller rotatably mounted near the base of the reel compartment, an eccentric roller rotatably mounted near the base of the reel compartment and spacedly positioned from the idler roller, said idler roller and eccentric roller coacting to rotatably support the reel in the reel compar ment, said eccentric roller serving to jar the reel and coaxial unit carried thereby upon each revolution of the roller, and an electric motor provided for rotating the eccentric roller at a predetermined speed, whereby when the eccentric roller is rotated the coaxial unit is rotated and jarred thereby to cause any faults therein to be so positioned between the conductors of the coaxial unit that the potential difference between the con ductors will break down the faults and indicate the presence of such faults in the coaxial unit.

2. In a testing apparatus arranged to impress across the filamentary central conductor and the outer tubular conductor of a coaxial unit a D. C. potential having an intensity sufficient to break down any faults which provide paths of reduced dielectric strength between the conductors, the improvement which comprises a reel compartment in which a reel containing a length of coaxial unit may be positioned, a flexible cable properly connected to the testing apparatus and suspended in the reel compartment for connectin the inner end of the central conductor of the ;co.- axial unit to the testing apparatus and thereby impress the D. C. potential across :the conductors of the coaxial unit, and idler roller rotatably mounted near the base of the reel compartment an eccentric roller rotatably mounted .near the base of the reel compartment, said idlerroller-and eccentric roller being spacedly positioned with respect to each other so as to rotatably support the reel above the base of the reel compartment, said eccentric roller serving to rotateand jar the coaxialunit carried on'the reel upon eachrrevolution of the rollenmeans iorlrotatingv the eccentric roller at a predetermined speed whereby the co axial unit is rotated and jarred to cause any faults therein to be so positioned between the conductors that the potential difference between 8 the conductors will "break down the fault and indicate the presence of such faults in-the coaxial unit, and timing means electrically connected to terminate the operation of the rotating means after the coaxial .unit has been rotated and jarred a vpredeteri'nined number of times.

SAM BOCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

